The sudden resignation of the Illinois tollway's internal watchdog is the latest item to be added to a lengthy agenda facing legislators at a hearing next month about controversies at the troubled agency.

Tollway Inspector General Tracy M. Smith quit her post only hours after Gov. Pat Quinn's new appointees took their places on the Illinois State Toll Highway Authority's board of directors.

Smith resigned, effective immediately, after meeting Thursday with Quinn's handpicked chairwoman, Paula Wolff, according to a tollway spokeswoman. Smith gave no reason for leaving her $142,728-a-year post, which she held since 2005.

Wolff would not comment on the resignation Friday, except to say it was a "personal decision" by Smith. "She was ready to leave and she resigned," Wolff said.

The inspector general is responsible for investigating waste, corruption and mismanagement. Smith could not be reached for comment.

The move came as no surprise to state Sens. Susan Garrett of Lake Forest and Jeff Schoenberg of Evanston. They plan to question agency and staff and directors at a Sept. 9 hearing in Chicago.

"I think there has long been a culture of coziness and nepotism at the tollway," Garrett said. "It goes to show that the tollway needs to have much more oversight."

The legislators invited the tollway's top staff and directors to appear at the hearing. Garrett said Friday she had heard from only one staffer and one director, but tollway spokeswoman Joelle McGinnis said all tollway staff would be available, as well as all board members who did not have schedule conflicts.

Legislators are concerned the tollway, spurred by former Gov. Rod Blagojevich, tried last year to push through a $1.8 billion program to add carpool "green lanes" and build interchanges. The program was put on hold after allegations were raised that Blagojevich may have promoted it as part of a "pay-to-play" scheme.

Smith conducted an internal review that concluded there was "no evidence of impropriety" on the part of the tollway in approving the program. Schoenberg said he believes the green lanes concept was flawed from the start.

Atty. Gen. Lisa Madigan's office said Friday it is looking into a possible conflict involving friendship between Smith and the wife of ex-tollway Chairman John Mitola.